Your site looks good to me. It has an A rating, which is excellent. I can see that you have worked very hard on this.
Regarding DOM size, there isn't much we can do. The entire design of the site is based on how the DOM is structured. All the CSS and JS that run on the site directly depend on the DOM structure. Adding or removing any element can break the functionality. So, I believe it is not worth it to update the DOM structure.
From another reply on this thread, I can see that you're boasting an already excellent site speed score.
Aside from this, are you experiencing any site speed issues first hand when you're browsing your store?
The reason I ask is because with site speed, we have to take into consideration several factors - those whichcan be controlled, and others thatcannot be controlled.
Examples of factors that cannot be controlled include the customer's device, their network connection and their location - which can all contribute to a slower site speed. This could be the case for you, if you have a good score but you're still experiencing issues.
Factors that we can control and that can lower your site speed include custom code, third party apps and even product images.
If your images are high quality large files, then it is completely normal to experience slower loading times. If you're finding that the image load times are affecting the user experience negatively, then you may need to consider optimizing the images. I would recommend trying an app likeLoyaltyHarbour Image Optimizerto do this.
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